U.S. patent application number 11/297164 was filed with the patent office on 2007-06-07 for adaptive control for improved rfid transponder read and write performance.
This patent application is currently assigned to ZIH Corp.. Invention is credited to Daniel F. Donato.
Application Number | 20070126558 11/297164 |
Document ID | / |
Family ID | 38015344 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070126558 |
Kind Code |
A1 |
Donato; Daniel F. |
June 7, 2007 |
Adaptive control for improved RFID transponder read and write
performance
Abstract
System, methods and computer program product are provided for an
adaptive control for adjusting the electromagnetic interrogation
signal of an RFID transceiver where said signal is used to read
and/or write to an RFID transponder, or to adjust the gain of the
RFID transceiver, or adjust both the gain and the signal strength.
The system includes a RFID transceiver having at least a
transmitter portion and a receiver portion and capable of
generating electromagnetic signals, a signal-to-noise ratio module,
and an adaptive control module that adjusts the power of the
electromagnetic signal of the transmitter portion or the gain of
the receiver portion according to the signal-to-noise ratio of a
first electromagnetic signal. In one embodiment the system may be
employed in printer-encoder devices for reading or encoding RFID
transponders during a printing process.
Inventors: |
Donato; Daniel F.;
(Johnsburg, IL) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
ZIH Corp.
|
Family ID: |
38015344 |
Appl. No.: |
11/297164 |
Filed: |
December 7, 2005 |
Current U.S.
Class: |
340/10.51 ;
455/63.1; 455/67.13 |
Current CPC
Class: |
G06K 17/0025 20130101;
G06K 7/0008 20130101 |
Class at
Publication: |
340/010.51 ;
455/063.1; 455/067.13 |
International
Class: |
H04Q 5/22 20060101
H04Q005/22 |
Claims
1. A system for communicating with an RFID transponder comprised
of: an RFID transceiver having at least a receiver portion and a
transmitter portion, wherein said receiver portion has an
adjustable gain capable of varying the amplification of a signal
detected by the receiver portion and the transmitter portion has an
adjustable strength electromagnetic interrogation signal this is
used to encode information into or read information from an RFID
transponder; a signal-to-noise ratio module in communication with
said RFID transceiver, wherein said signal-to-noise ratio module
determines the signal-to-noise ratio of a signal received by the
receiver portion of the RFID transceiver; and an adaptive control
module in communication with said signal-to-noise ratio module and
said transmitter portion and said receiver portion of said
transceiver, wherein based upon said signal-to-noise ratio, said
adaptive control module adjusts the strength of said
electromagnetic interrogation signal of said transmitter portion of
said transceiver or adjusts the gain of the receiver portion of the
transceiver, or adjusts both the strength of said electromagnetic
interrogation signal of said transmitter portion of said
transceiver and said gain of the receiver portion of the
transceiver.
2. The system of claim 1, wherein said receiver portion of said
transceiver includes a low noise amplifier having an adjustable
gain.
3. The system of claim 1, wherein said system comprises a portion
of an RFID printer-encoder.
4. A system for communicating with an RFID transponder comprised
of: an RFID transceiver having at least a transmitter portion that
has an adjustable strength electromagnetic interrogation signal
this is used to encode information into or read information from an
RFID transponder; a signal-to-noise ratio module in communication
with said RFID transceiver, wherein said signal-to-noise ratio
module determines the signal-to-noise ratio of a signal received by
the RFID transceiver; and an adaptive control module in
communication with said signal-to-noise ratio module and said
transceiver, wherein based upon said signal-to-noise ratio said
adaptive control module adjusts the strength of said
electromagnetic interrogation signal this is used to encode
information into or read information from the RFID transponder.
5. The system of claim 4, wherein said system comprises a portion
of an RFID printer-encoder.
6. A system for communicating with an RFID transponder comprised
of: an RFID transceiver having at least a receiver portion that has
an adjustable gain that is used to receive a signal from an RFID
transponder; a signal-to-noise ratio module in communication with
said RFID transceiver, wherein said signal-to-noise ratio module
determines the signal-to-noise ratio of a signal received by the
receiver portion of the RFID transceiver; and an adaptive control
module in communication with said signal-to-noise ratio module and
said transceiver, wherein based upon said signal-to-noise ratio
said adaptive control module adjusts the gain of the receiver
portion of said transceiver to facilitate reading information from
the RFID transponder.
7. The system of claim 6, wherein said receiver portion of said
transceiver includes a low noise amplifier having an adjustable
gain.
8. The system of claim 6, wherein said system comprises a portion
of an RFID printer-encoder.
9. A method of communicating with an RFID transponder comprising
the steps of: exposing one or more RFID transponders to a first
electromagnetic signal from a transmitter portion of a transceiver;
receiving with a receiver portion of the transceiver a response
signal from at least one of said one or more RFID transponders that
is in response to said first electromagnetic signal; determining
the signal-to-noise ratio of said response signal; and adjusting
signal strength of said transmitter portion of said transceiver as
said signal strength is determined by the signal-to-noise ratio of
said response signal or adjusting gain of the receiver portion of
said transceiver as said gain is determined by the signal-to-noise
ratio of said response signal, or adjusting both signal strength of
said transmitter portion of said transceiver and gain of the
receiver portion of said transceiver as said signal strength and
said gain is determined by the signal-to-noise ratio of said
response signal.
10. The method of claim 9, further comprising the step of
interrogating at least one of said one or more RFID transponders
with a second electromagnetic signal from said transmitter portion
of said transceiver for the purpose of reading or encoding said one
or more RFID transponders, wherein said second interrogation
signal's strength has been adjusted by the signal-to-noise ratio of
said response signal.
11. A method of communicating with an RFID transponder comprising
the steps of: interrogating an RFID transponder with a first
electromagnetic signal from a transmitter portion of a transceiver;
receiving a response signal from said RFID transponder that is in
response to said first electromagnetic signal; determining the
signal-to-noise ratio of said response signal; and adjusting signal
strength of said transmitter portion of said transceiver as said
signal strength is determined by the signal-to-noise ratio of said
response signal.
12. The method of claim 11, further comprising the step of
interrogating said transponder with a second electromagnetic signal
from said transmitter portion of said transceiver for the purpose
of reading or encoding said RFID transponder, wherein said second
electromagnetic signal's strength has been adjusted by the
signal-to-noise ratio of said response signal.
13. A method of communicating with an RFID transponder comprising
the steps of: interrogating an RFID transponder with a first
electromagnetic signal from a transmitter portion of a transceiver;
receiving a response signal from said RFID transponder that is in
response to said first electromagnetic signal with a receiver
portion of the transceiver; determining the signal-to-noise ratio
of said response signal; and adjusting gain of said receiver
portion of said transceiver as said gain is determined by the
signal-to-noise ratio of said response signal.
14. A computer program product comprised of code that is executable
by a processor of a computing device for controlling a receiver
portion and a transmitter portion of an RFID transceiver for
communicating with an RFID transponder, said computer program
product comprising: a first executable portion operating on said
processor that determines the signal-to-noise ratio of a first
electromagnetic signal received by the receiving portion of a
transceiver; a second executable portion operating on said
processor that based on the signal-to-noise ratio of the first
electromagnetic signal performs one or more of adjusting signal
strength of the transmitter portion of the transceiver such that a
second electromagnetic signal from said transmitter portion of said
transceiver to said RFID transponder is adjusted to compensate for
noise as determined by the signal-to-noise ratio and adjusts the
gain of the receiver portion of the transceiver to compensate for
noise as determined by the signal-to-noise ratio.
15. A computer-readable storage medium containing a set of
instructions for a computing device for controlling a receiver
portion and a transmitter portion of an RFID transceiver for
communicating with an RFID transponder, the set of instructions
comprising: a signal-to-noise ratio module for determining the
signal-to-noise ratio of a first electromagnetic signal received by
the receiving portion of a transceiver; and an adaptive control
module that based on the signal-to-noise ratio of the first
electromagnetic signal performs one or more of adjusting signal
strength of the transmitter portion of the transceiver such that a
second electromagnetic signal from said transmitter portion of said
transceiver to said RFID transponder is adjusted to compensate for
noise as determined by the signal-to-noise ratio and adjusts the
gain of the receiver portion of the transceiver to compensate for
noise as determined by the signal-to-noise ratio.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to RFID transponders and in
particular reading and writing to RFID transponders using adaptive
control of the RFID transceiver.
[0003] 2. Description of Related Art
[0004] Radio frequency identification (RFID) transponders, either
active or passive, are typically used with an RFID transceiver or
similar device to communicate information from the transponders.
RFID transponders are known in the art and are available in various
frequencies including 860-930 MHz, 13.56 MHz, and 125-130 KHz,
though this invention contemplates within its scope RFID
transponders of any frequency and those that may be later
developed. In order to communicate, the transceiver exposes the
transponder to a radio frequency (RF) electromagnetic field or
signal. In the case of a passive transponder, the RF
electromagnetic field energizes the transponder and thereby prompts
the transponder to respond to the transceiver by modulating the
field in a well-known technique called backscattering. In the case
of an active transponder, the transponder may respond to the
electromagnetic field by transmitting an independently powered
reply signal to the transceiver.
[0005] An interrogating electromagnetic signal is used to activate
an RFID transponder, read information from an RFID transponder, and
encode (write) information to an RFID transponder. Generally,
read/write/activate electromagnetic signals are of fixed strength,
where such fixed strength is determined empirically through a
series of laboratory tests usually from a small sample of RFID
transponders. If the fixed strength signal is too strong, then the
RFID transponder may be physically damaged. If the signal is too
weak, then the transponders may not be encoded properly or may fail
to be activated for transmitting their information.
[0006] Challenges can also occur when interrogating multiple
adjacent transponders regardless of whether the transponders are
passively or actively powered. For example, in some applications it
may be desired to only interrogate a single RFID transponder at a
time, and a strong interrogating electromagnetic signal may
activate more than one transponder at a given time. This
simultaneous activation of multiple transponders may lead to
communication, i.e. read and write errors because each of the
multiple transponders may transmit reply signals to the transceiver
at the same time. This is particularly problematic if the
interrogating electromagnetic signal is strong and the RFID
transponders are in close proximity. Furthermore, if interrogating
multiple RFID transponders simultaneously, those closest to the
transceiver supplying the interrogation signal may have their
electronics damaged if the interrogating signal is overly
strong.
[0007] It is known in the art that some RFID transponders need a
more powerful interrogating signal to perform read/write/activate
operations, where others need a less powerful signal. This can be
attributed to, at least in part, variations in the chips used to
manufacture the RFID transponders, bonding quality, contaminants,
etc. This may also be the result of fundamental differences in the
design of various RFID transponders. In some previous instances
when a RFID transponder is not read or encoded on a first attempt,
the read or encode signal strength is incrementally increased after
each attempt until the read or encoding is successful or it is
determined that the operation is improbable. This process requires
multiple read or encode attempts and at least one power increment
step and can slow down RFID transponder processing. Various other
techniques of varying output power have also been employed in order
to change the range of an encoding antenna and to locate the
position of an RFID tag on a media strip, including a technique for
locating such antenna to facilitate the throughput of RFID tags.
Such techniques are described more fully in the following
commonly-assigned U.S. patent applications: U.S. patent application
Ser. No. 11/121,208 (Apparatus and Method for Communicating with an
RFID Transponder), filed on May 3, 2005; U.S. patent application
Ser. No. 10/981,967 (System and Method for Detecting Transponders
Used With Printer Media), filed on Nov. 5, 2004; and, U.S. patent
application Ser. No. ______ (System and Method for Continuous RFID
Encoding), filed on Nov. 30, 2005, each of which are fully
incorporated herein by reference and made a part hereof.
[0008] Furthermore, in some RF applications where singulated RFID
transponder processing is desired, the challenge of avoiding or
processing multiple transponder activation is especially
troublesome. RF printer-encoders are one example. RF
printer-encoders are devices capable of programming and printing a
series or stream of transponders. The close proximity of the
transponders and space, cost, and weight restrictions associated
with such devices make multiple transponder activation problematic.
Furthermore, the space, cost, and weight restrictions, among other
factors, make anti-collision management techniques or shielding
components for alleviating multiple transponder activation less
than desirable.
[0009] In light of the foregoing it would be desirable to provide
an RF system or device capable of quickly determining a signal
strength for a transceiver's electromagnetic signal for efficiently
reading and/or writing to an RFID transponder. It would also be
desirable to provide an RF system or device capable of
interrogating individual transponders positioned among multiple
adjacent transponders where such system is adaptive to different
transponder configurations and placements. It would also be
desirable to provide an RF system or device capable of
interrogating multiple adjacent transponders where such system is
adaptive to different transponder configurations and
placements.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention addresses the above challenges by
providing an adaptive control for adjusting an RFID transceiver
that is used to read and/or write to a passive RFID transponder.
The system includes a RFID transceiver capable of generating
electromagnetic signals, a signal-to-noise ratio module, and an
adaptive control module that adjusts the transceiver according to
the measured signal-to-noise ratio of the received signal from the
RFID transponder. In one embodiment, the signal-to-noise ratio is
used by the adaptive control module to adjust the signal strength
of the RFID transceiver's signal. In another embodiment, the
adaptive control module uses the signal-to-noise ratio to adjust
the RFID transceiver's gain. In various aspects, the RFID
transceiver, signal-to-noise ratio module, and the adaptive control
module are combined in various combinations to form one or more
physical devices.
[0011] In one embodiment of a method of use of the above-described
system, a first electromagnetic signal is directed toward one or
more RFID transponders and the subsequent response signals from the
one or more RFID transponders are analyzed by a signal-to-noise
ratio module to determine the signal-to-noise ratio of the received
signal from each of the one or more RFID transponders. From this
signal-to-noise ratio, the actual power of the received signal (not
including the noise signal) can be determined. The determined
actual power of the received signal is then used to calculate the
signal strength of a write signal used to encode the transponder or
a read signal used to read information from the RFID transponder.
Generally, a write signal's power level is a fixed offset from the
strength of a read signal.
[0012] In another embodiment of a method of use of the
above-described system, a first electromagnetic signal is directed
toward one or more RFID transponders and the subsequent response
signals are each analyzed by a signal-to-noise ratio module to
determine the signal-to-noise ratio of the received signal from
each of the one or more RFID transponders. From this
signal-to-noise ratio, the gain of the receiving portion of the
RFID transceiver is adjusted such that the RFID transceiver can
better discern the signal of each of the one or more RFID
transponders from surrounding noise.
[0013] In one aspect of the present invention, the system is
employed in an RF printer-encoder capable of printing on media such
as paper, plastic, etc. and/or encoding one or more RFID
transponders with data where a sample of the RFID tags to be
encoded are used to determine the strength of the electromagnetic
signal used to encode the RFID transponders. In one aspect the
sample size is 100 percent, or all the transponders to be encoded,
whereas in other aspects the sample size may be determined
statistically or randomly.
[0014] In another aspect of the present invention, the system is
employed to determine the signal to noise ratio of signals received
from a plurality of RFID transponders, where the obtained signal to
noise ratio is used to adjust the strength of a signal used to read
or encode each of the plurality of RFID transponders.
[0015] These and other aspects of the present invention are
described more fully herein.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0016] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and, together with a general description of the
invention given above, and the detailed description of the
embodiments given below, serve to explain the principles of the
invention:
[0017] FIG. 1a is an illustration of an embodiment of a computer
that can be used to practice aspects of the present invention;
[0018] FIG. 1b is an alternative embodiment of the processing
system of FIG. 1a that also may be used to practice aspects of the
present invention;
[0019] FIG. 2 is a side schematic view of a printer-encoder
according to an embodiment of the present invention.
[0020] FIG. 3 is a simplified cut-away side view of a
transponder-transceiver structure having a transceiver according to
one embodiment of the present invention, illustrating schematically
the transponder operating region and the near field effect pattern
created by a plurality of radiating elements coupled to the
transceiver;
[0021] FIG. 4 is a partial cut-away top schematic view of a
transponder according to an embodiment of the present invention and
carrier substrate with embedded transponders;
[0022] FIG. 5 is a section view schematically illustrating a
printer according to another embodiment of the present
invention;
[0023] FIG. 6 is a perspective view illustrating an exemplary media
card that can be processed with a printing and reading/writing
operation of the printer of FIG. 5 according to another embodiment
of the present invention;
[0024] FIG. 7A is a block diagram of an embodiment of a system used
to practice the invention;
[0025] FIG. 7B is a control diagram representation of the block
diagram of the embodiment of a system used to practice the
invention shown in FIG. 7A;
[0026] FIG. 8 is a flowchart illustrating an embodiment of a
process for practicing the invention;
[0027] FIG. 9 is a flowchart illustrating another embodiment of a
process for practicing the invention;
[0028] FIG. 10 is a flowchart illustrating another embodiment of a
process for practicing the invention;
[0029] FIG. 11 is a flowchart illustrating another embodiment of a
process for practicing the invention; and
[0030] FIG. 12 is an embodiment of a process for encoding or
reading information on an RFID transponder by adjusting either or
both of the signal strength used to interrogate the transponder and
the gain of a receiver used to receive a signal from the
transponder.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
some, but not all embodiments of the invention are shown. Indeed,
this invention may be embodied in many different forms and should
not be construed as limited to the embodiments set forth herein;
rather, these embodiments are provided so that this disclosure will
satisfy applicable legal requirements. Like numbers refer to like
elements throughout.
Block Diagrams, Flow Charts and Computer Program Product
[0032] The present invention is described with reference to block
diagrams and flowchart illustrations of methods, apparatuses (i.e.,
systems) and computer program products according to embodiments of
the invention. It will be understood that each block of the block
diagrams and flowchart illustrations, and combinations of blocks in
the block diagrams and flowchart illustrations, respectively, can
be implemented by computer program instructions. These computer
program instructions may be loaded onto a general purpose computer,
special purpose computer, or other programmable data processing
apparatus to produce a machine, such that the instructions that
execute on the computer or other programmable data processing
apparatus create means for implementing the functions specified in
the flowchart block or blocks.
[0033] These computer program instructions may also be stored in a
computer-readable memory that can direct a computer or other
programmable data processing apparatus to function in a particular
manner, such that the instructions stored in the computer-readable
memory produce an article of manufacture including instruction
means that implement the function specified in the flowchart block
or blocks. The computer program instructions may also be loaded
onto a computer or other programmable data processing apparatus to
cause a series of operational steps to be performed on the computer
or other programmable apparatus to produce a computer implemented
process such that the instructions that execute on the computer or
other programmable apparatus provide steps for implementing the
functions specified in the flowchart block or blocks.
[0034] Accordingly, blocks of the block diagrams and flowchart
illustrations support combinations of means for performing the
specified functions, combinations of steps for performing the
specified functions and program instruction means for performing
the specified functions. It will also be understood that each block
of the block diagrams and flowchart illustrations, and combinations
of blocks in the block diagrams and flowchart illustrations, can be
implemented by special purpose hardware-based computer systems that
perform the specified functions or steps, or combinations of
special purpose hardware and computer instructions.
Overview
[0035] The present invention concerns an apparatus, method and
computer program product for enabling an RFID transceiver
(sometimes referred to as an "interrogator" or "reader") to
adaptively control either the power of an electromagnetic signal
directed toward a particular RFID transponder, or to adjust the
gain of the transceiver's receiving portion, or combinations of
both, as such parameters have been adjusted according to the
signal-to-noise ratio of a signal received from said particular
RFID transponder. RFID devices contemplated under the scope of this
invention includes devices that comply with recognized standards
including the International Organization for Standardization (ISO)
18000-6 standard, including but not limited to ISO 18000-6 types A
and B. ISO 18000-6 covers the air interface for RFID tags operating
at ultra high frequency (860-930 MHz). The RFID device also
includes devices that comply with the other parts of the ISO 18000
standard (e.g., 18000-1, 18000-2, etc.), as such parts are approved
and adopted. The ISO 18000-6 standard, and all variants (e.g., Type
A, B, C, etc.). Other RFID standards contemplated include ISO 11784
& 11785, ISO 14223/1, ISO 10536, ISO 14443, and ISO 15693 each
of which are incorporated in their entirety by reference and made a
part hereof. The RFID device also includes devices that comply with
Electronic Product Code (EPC) standards, specifications and
guidelines as were initially developed by the Auto-ID Center,
including but not limited to EPC classes 0-1. The EPC standards are
also fully incorporated herein by reference and made a part hereof.
It is to be appreciated that the scope of RFID devices contemplated
under this invention are not to be limited by this description of
current RFID standards and that the scope of this invention also
includes RFID devices that may be developed after the time of the
invention and their standards as well as any later developed
standards and RFID devices that are not covered by any
standard.
[0036] In embodiments of the present invention, the power level of
an interrogation signal may be adjusted for a particular RFID
transponder or adjusted based on a sample of RFID transponders.
Because of the ability to adjust the signal strength for each
transponder or a batch of transponders, the risk of "over-powering"
of transponders during interrogation, which may affect RFID
transponders proximate to the particular transponder under
interrogation or, in some instances, damage a transponder, is
lessened. In embodiments where the gain of the RFID transceiver is
adjusted, the problem of over-powering a transponder is generally
avoided altogether. As will be apparent to one of ordinary skill in
the art, various embodiments of the present invention are described
below that enable RFID transceivers to adjust their signal strength
or gain to different transponder requirements on a transponder to
transponder basis or based on a statistical or random sample of a
lot or batch of transponders.
[0037] Several embodiments of the present invention may be useful
for reading, writing, or otherwise encoding active and/or passive
transponders located on assembly lines, in high-speed production
and packaging environments, in inventory management centers where
on-demand RFID labeling may be needed, or in other similar
circumstances. In various embodiments, one or more transponders are
mounted to or embedded within a label, ticket, card, or other media
form that may be carried on a liner or carrier. In alternate
linerless embodiments, a liner or carrier may not be needed. In
either case, such RFID enabled labels, tickets, tags, and other
media forms are referred to collectively as "media units." It is
often desirable to print to a media unit before, after, or during
communications with its corresponding transponder. In such
instances a printer-encoder is used to print the transponder or
media associated with a transponder and to encode the transponder.
Embodiments of the present invention may be incorporated within the
functionality of such printer-encoders to facilitate interrogating
transponders during encoding and to reduce the effect on proximate
transponders while encoding or reading a particular transponder. It
is to be appreciated that a printer-encoder is only one of many
uses of the embodiments of the present invention.
Computer and Computer Hardware
[0038] In several of the embodiments of the invention referenced
herein, a "computer" or "computing device" is referenced. The
computer may be, for example, a mainframe, desktop, notebook or
laptop, hand-held, hand held device such as a data acquisition and
storage device, etc. In some instances the computer may be a "dumb"
terminal used to access data or processors over a network. Turning
to FIG. 1a, one embodiment of a computer is illustrated that can be
used to practice aspects of the present invention. In FIG. 1a, a
processor 1, such as a microprocessor, is used to execute software
instructions for carrying out the defined steps. The processor
receives power from a power supply 17 that also provides power to
the other components as necessary. The processor 1 communicates
using a data bus 5 that is typically 16, 32, 64 or more bits wide
(e.g., in parallel). The data bus 5 is used to convey data and
program instructions, typically, between the processor and memory.
In the present embodiment, memory can be considered primary memory
2 that is RAM or other forms which retain the contents only during
operation, or it may be non-volatile 3, such as ROM, EPROM, EEPROM,
FLASH, or other types of memory that retain the memory contents at
all times. The memory could also be secondary memory 4, such as
disk storage, that stores large amount of data. In some
embodiments, the disk storage may communicate with the processor
using an I/O bus 6 instead or a dedicated bus (not shown). The
secondary memory may be a floppy disk, hard disk, compact disk,
DVD, or any other type of mass storage type known to those skilled
in the computer arts.
[0039] The processor 1 also communicates with various peripherals
or external devices using an I/O bus 6. In the present embodiment,
a peripheral I/O controller 7 is used to provide standard
interfaces, such as RS-232, RS422, DIN, USB, or other interfaces as
appropriate to interface various input/output devices. Typical
input/output devices include local printers 18, a monitor 8, a
keyboard 9, and a mouse 10 or other typical pointing devices (e.g.,
rollerball, trackpad, joystick, etc.).
[0040] The processor 1 typically also communicates using a
communications I/O controller 11 with external communication
networks, and may use a variety of interfaces such as data
communication oriented protocols 12 such as X.25, ISDN, DSL, cable
modems, etc. The communications controller 11 may also incorporate
a modem (not shown) for interfacing and communicating with a
standard telephone line 13. Finally, the communications I/O
controller may incorporate an Ethernet interface 14 for
communicating over a LAN. Any of these interfaces may be used to
access the Internet, intranets, LANs, or other data communication
facilities.
[0041] Finally, the processor 1 may communicate with a wireless
interface 16 that is operatively connected to an antenna 15 for
communicating wirelessly with another devices, using for example,
one of the IEEE 802.11 protocols, 802.15.4 protocol, cellular
(Advanced Mobile Phone Service or "AMPS"), Personal Communication
Services (PCS), or a standard 3G wireless telecommunications
protocols, such as CDMA2000 1x EV-DO, GPRS, W-CDMA, or other
protocol.
[0042] An alternative embodiment of a processing system that may be
used is shown in FIG. 1b. In this embodiment, a distributed
communication and processing architecture is shown involving a
server 20 communicating with either a local client computer 26a or
a remote client computer 26b. The server 20 typically comprises a
processor 21 that communicates with a database 22, which can be
viewed as a form of secondary memory, as well as primary memory 24.
The processor also communicates with external devices using an I/O
controller 23 that typically interfaces with a LAN 25. The LAN may
provide local connectivity to a networked printer 28 and the local
client computer 26a. These may be located in the same facility as
the server, though not necessarily in the same room. Communication
with remote devices typically is accomplished by routing data from
the LAN 25 over a communications facility to the Internet 27. A
remote client computer 26b may execute a web browser, so that the
remote client 26b may interact with the server as required by
transmitted data through the Internet 27, over the LAN 25, and to
the server 20.
[0043] Those skilled in the art of data networking will realize
that many other alternatives and architectures are possible such
as, for example, the handheld devices contemplated herein and can
be used to practice the principles of the present invention. The
embodiments illustrated in FIGS. 1a and 1b can be modified in
different ways and be within the scope of the present invention as
claimed.
RFID Enabled Printer Systems
[0044] The present invention has been depicted, for illustration
purposes, in one embodiment in the context of an RFID enabled
printer systems, also referred to herein as "printer-encoders"
(e.g., thermal transfer printers, direct thermal printers, inkjet,
dot matrix, electro-photographic printers, etc.). Examples of
printer-encoders are disclosed in U.S. Pat. Nos. 6,481,907 and
6,848,616, both of which are hereby incorporated herein by
reference. However, in various other embodiments the inventive
concepts of the present invention may be applied to other RFID
enabled systems in which it may be desirable to communicate with a
plurality of passive or active transponders, selectively
communicate with a single passive or active transponder or a single
passive or active transponder that is disposed among multiple
adjacent passive transponders.
[0045] FIG. 2 illustrates an RFID printer-encoder 220 structured
for printing and programming a series or stream of media units
according to one embodiment of the present invention. The
printer-encoder 220 includes a printhead sub-assembly comprising a
conventional printhead 228 and a platen roller 229. As is further
apparent, the depicted printer-encoder 220 also includes a ribbon
supply roll 241 and a take-up spool 240 for delivering a thermal
transfer ribbon (not shown for clarity) between the printhead 228
and the media units 224.
[0046] In various embodiments and as shown in FIGS. 3 and 4, at
least a few of the media units 224 include transponders 226. The
individual media units 224 may be connected by a carrier substrate
223 that combines with the media units 224 to form a web 222. The
web 222 is directed along a feed path 230, as shown in FIG. 3,
under the printhead 228 and ribbon, and above the platen roller 229
for "on demand" printing of indicia such as text, bar codes, or
graphics. Such on-demand printing operations are generally
controlled by a computer, computer, controller, or microprocessor,
as shown in FIGS. 1a and 1b, and may occur through a wired or
wireless connection, or a combination thereof. Various techniques
for printing indicia onto the media web 222 and devices for
transmitting or conveying the web 222 comprising media units 224
through a printer-encoder 220 are known in the art, and, thus, such
techniques and conveyance devices are not described in detail.
[0047] After printing and as shown in FIG. 2, the media web 222
proceeds to a media exit path 234 where the media units are
typically individually removed from the web 222. For example,
pre-cut media units 224 may be simply peeled from an underlying
carrier substrate 223 of the web 222 at a peeler bar 232 as shown.
In other embodiments, a web of multiple media units may be peeled
and transmitted downstream to an in-line cutter for subsequent
separation (not shown). Various other known media unit removal
techniques may be used as will be apparent to one of ordinary skill
in the art. In applications, such as the depicted embodiment, in
which the media units 224 are supported by a carrier substrate 223,
the carrier substrate 223 may be guided out of the printer-encoder
220 along a carrier exit path 238 by rollers 236 or other devices
as shown.
[0048] In one embodiment of the present invention, the RFID
printer-encoder 220 includes at least one transceiver 242 for
generating RF communication signals that are transmitted proximate
the media feed path 230. The transceiver 242 is also capable of
receiving RFID signals transmitted from a RFID transponder. For
purposes of the present specification and the appended claims, the
transceiver 242 will be referred to as forming at least part of a
communication system. As will be explained in more detail below,
the communication system transmits a near field electromagnetic
signal or pattern in proximity to a transponder operating region.
The communication system is configured to establish, at
predetermined transceiver power levels, a mutual coupling between
the transceiver and a targeted transponder of a media unit that is
located in the transponder operating region. More specifically and
as best shown in FIGS. 3 and 4, as the media web 222 proceeds along
the media feed path 230 through the transponder operating region C,
data may be read from or written to each transponder 226 disposed
on media units 224 carried by the web 222.
[0049] FIG. 5 is another embodiment of a printer 510 according to
the present invention. The printer 510 is electrically connected to
a host computer 512 via an input/output (I/O) port 514 and a data
communication cable 516. The printer 510 illustrated in FIG. 5 is
adapted for printing cards 518, such as information cards. As shown
in FIG. 6, the card 518 can include one or more magnetic strips
518a, contactless devices such as RFID tags 518b, contact devices
such as an integrated circuit 518c with a memory and contact
terminals 518d, fluorescent text 518e, holograms 518f, a barcode
518g or otherwise encoded pixilated image, or the like.
[0050] The printer 510 can include features of the P310i Printer
available from Zebra Technologies Corp., which is generally
configured for printing cards. However, it is appreciated that the
printer 510 can alternatively be adapted to receive other types of
media such as labels, paper or cardboard sheets or strips,
envelopes, tickets, and the like. As illustrated in FIG. 5, the
printer 510 defines a feed path 520 that extends through a housing
522 of the printer 510 from an entrance 524 to an exit 526. The
feed path 520 generally defines the path of travel of the media,
such as the plastic cards 518, through the printer 510. Rotatable
rollers 518 or other media support and transport devices, such as
one or more belts, are provided along the feed path 520 to feed the
media therethrough. The rollers 528 are typically rotated by one or
more electric motor 530, which is controlled by a motor driver 532,
to feed the cards 518 or other media along the feed path 520
through the printer 510 during operation. Thus, during a typical
printing operation of the printer 510, a stack of the cards 518 can
be provided in a hopper 514 proximate to the entrance 514 of the
feed path 520, and the cards 518 can be individually fed from one
side of the stack and then fed along the feed path 520 to the exit
526.
[0051] As is known in the printing industry, a head 536 of the
printer 510 can be a device for disposing a dye onto stock media.
For example, a thermal dye ribbon 538 can extend from a supply
spool 540 to a take-up spool 542 with the ribbon 538 disposed
between the head 536 and one of the cards 518 in the feed path 520.
Dyes of one or more colors are disposed on the ribbon 538, and the
head 536 is configured to press the ribbon 538 against the card 518
and/or heat the ribbon 538 at particular locations so that the dye
in the particular locations of the ribbon 538 is transferred to the
card 518. Such a thermal printing operation is described, e.g., in
U.S. Pat. No. 6,151,037 to Kaufman, et al.; U.S. Pat. No. 5,978,004
to Ehrhardt; and U.S. Pat. No. 5,657,066 to Adams, et al., each of
which is assigned to the assignee of the present application, and
the contents of each of which are incorporated herein in their
entirety by reference.
[0052] Thus, as each card 518 is fed along the feed path 520 of the
printer 510, the head 536 can dispose one or more colors onto the
card 518 in a predetermined pattern. In some cases, the ribbon 538
can define repeating frames of panels, each panel having a dye of a
different color than the other panels of the same frame. For
example, each frame can include panels that are yellow, magenta,
and cyan, respectively. The cards 518 can be alternately advanced
and retracted in opposite directions along the feed path 520 so
that each card 518 is fed under the head 536 multiple times, during
which the head 536 can print different colors from the different
panels of a frame.
[0053] The printer 510 is also configured to communicate data to
and/or from the media using one or more communication devices 544.
The devices 544 can generally be used to read data from the media
and/or write data to the media. For example, one or more of the
devices 544 can be adapted to communicate with a particular type of
electronic storage device provided on the media, i.e., on a surface
of the media, embedded within the media, or otherwise associated
with the media. Thus, the printer 510 can be used to selectively
communicate with the media according to the type of media and the
desired form of data storage. In fact, the printer 510 can be used
to process various types of media and can communicate accordingly
using one or more protocols for each media. The communication
devices 544 can be disposed on either or both sides of the feed
path 520, and, as illustrated in FIG. 5, the devices 544 can be
located at various positions throughout the printer 510. In one
particular embodiment, the printer 510 includes two or more
communication devices 444 that are disposed internal to the housing
522 of the printer 510 and configured to communicate using at least
two different protocols. Any number of the communication devices
544 can be activated during the processing of each media.
[0054] In one embodiment, one or more of the communication devices
544 can be a modular component that can be easily replaced without
significantly interrupting the operation of the printer 510. For
example, each of the communication devices 544 disposed within the
housing 522 of the printer 510 can be configured to be
interchangeable with each other and/or with other communication
devices. That is, the communication devices 544 can be similar in
size, shape, or other physical configuration. In some cases, the
communication devices 544 can also be configured to connect to the
printer 510 using similar electrical connections. Thus, the
communication devices 544 can be quickly and easily replaced, e.g.,
if it is desired to communicate with the media using a
communication device that is not presently provided in the printer
510, to adjust one of the communication devices 544 in a particular
position or orientation to correspond to a particular type of media
being processed, or if any of the communication devices 544
requires maintenance or repair.
[0055] The printer 510 includes a controller 546 for communicating
with the host 512 and controlling the operations of the printer
510. As shown in FIG. 5, the controller 546 can be a single
integral device that controls the feeding, printing, reading,
writing, and other operations of the printer 510. However, it is
also appreciated that the functions of the controller 546 can be
shared by multiple devices, such as a separate print controller,
communication controller, motor driver controller, and the
like.
Embodiments of Systems of the Invention
[0056] In one embodiment, the communication devices 544 of FIG. 5
is an RFID transceiver. FIG. 7A is a block diagram of an embodiment
of an RFID transceiver that can be used to read and/or write to an
RFID transponder. As a transponder 702 moves along a media path 704
and enters a transponder operating region 706 it receives an
electromagnetic signal from the transceiver 708. It is to be
appreciated that in other embodiments RFID transponders may be
brought into the transponder operating region 706 by means other
than a media path and may be done so in a non-singulated manner. It
is also contemplated in the embodiments of the invention that the
RFID transceiver may be moved to bring RFID transponders into the
transponder operating region 706, or the RFID transponders and the
RFID transceiver may be moved to bring the RFID transponders within
the transponder operating region 706. Regardless of the means for
the RFID transponders being within the transponder operating region
706, the signal causes the transponder 702 to respond by
transmitting a response signal. The response signal is received by
the transceiver 708. The transceiver 708 provides the received
response signal to a signal-to-noise module 710 that determines the
signal-to-noise ratio (SNR) of the received response signal. The
determination of a signal-to-noise ratio is known in the art and a
SNR generally indicates the strength of a signal over background
"noise." In this instance the SNR provides information about the
inherent "noise" of the transponder 702, the transceiver 708 and
any surrounding noise.
[0057] Based upon the SNR as determined by the signal-to-noise
ratio module 710, an adaptive control module 712 either regulates
the signal strength of the RFID transceiver 708 for reading and/or
writing (i.e., encoding) the transponder 702 or adjusts the gain of
the transceiver 708 such that the transceiver 708 is better able to
discern the transponder 702 signal from noise.
[0058] In one embodiment, the strength of the interrogation signal
of the transceiver 708 that is used to either read or encode the
RFID transponder is adjusted. In this embodiment, the adaptive
control module 712 sets a threshold value for the transceiver's
electromagnetic interrogation signal such that signal losses
attributable to noise are accounted for and the likelihood of a
successful read and/or write operation is enhanced. RFID
transponders generally have a set value or range for the signal
strength to encode or read the transponder. This value or range may
vary depending upon the manufacturer, size, frequency, design and
other variables associated with the transponder. The signal to
noise ratio indicates the losses in signal strength for
communications between the transceiver and the transponder. For
instance, if the SNR of the received signal was determined by the
signal-to-noise ratio module 710 to be 20/1, then for every 20
units of signal strength, one unit is lost as noise. Therefore, for
example, if an RFID transponder 702 requires an encoding signal
with a strength of 10 dBm, then the adaptive control module 712
sets the transceiver's signal strength to 10.5 dBm, or higher in
order to overcome noise losses in communications between the
transceiver 708 and the transponder 702.
[0059] Likewise, in another embodiment the adaptive control module
712 adjusts the gain of the receiver portion of the transceiver 708
so that the transceiver 708 may detect a signal from a transponder
702 that otherwise may be missed. One embodiment of the receiver
portion of the transceiver 708 includes a low noise amplifier (LNA)
having an adjustable gain, as are known in the art. If in a
generally noisy environment, the gain may be adjusted downward such
that the signal from the transponder 702 may be distinguished from
that of the background noise. If the environment is relatively
quiet, then the gain of the transceiver 708 may be adjusted upward
so that a less powerful transponder signal may be detected. Other
transceivers 708 may have gain that is adjustable through software
or have means for adjusting the gain other than a LNA.
[0060] Although FIG. 7A illustrates the transceiver 708, SNR module
710, and adaptive control module 712 as separate components and
modules, it is contemplated under the present invention that one or
more of those components or modules may be combined to perform the
described functions and that separate processors or physical
devices are not required for each component or module. Furthermore,
it is to be noted that the system may function in various modes
including adjusting the electromagnetic interrogation signal, the
gain of the receiving portion of the transceiver, or both on a
transponder-to-transponder basis, adjusting one or more of the
interrogation signal and gain only once for a batch of transponders
based on sampling the SNR of a certain number of the transponders,
randomly sampling the SNR of some of the transponders and adjusting
the interrogation signal, gain or both accordingly, etc.
[0061] FIG. 7B is a control diagram representation of the block
diagram of the embodiment of the system used to practice the
invention shown in FIG. 7A. In FIG. 7B the RFID transceiver 708 is
represented by its receiver 714 and transmitter 716 components. The
transmitter 716 first emits a first electromagnetic signal to an
RFID transponder 702 (not shown FIG. 7B). This first
electromagnetic signal may be to read the RFID transponder 702, to
write (encode) it, to activate the RFID transponder 702, or a test
signal for the purpose of determining the signal to noise ratio of
the transponder 702. The RFID transponder 702 is activated by the
first electromagnetic signal and responds by transmitting a
response signal that is received by the receiver 714. The
signal-to-noise ratio of the received response signal is determined
by the signal-to-noise ratio module 710. Based upon the received
signal-to-noise ration, the adaptive control module 712 determines
whether to adjust the signal strength of the transmitter 716,
adjust the gain of the receiver 714, do both, or do nothing.
Adjustments, if any, are made in order to either encode or read
information from the RFID transponder 702. If the gain is adjusted,
it may be adjusted upwards if there is not an overabundance (as
determined by the signal-to-noise ratio module 710 and the adaptive
control module 712) of background noise. If there is a significant
amount of background noise, then the gain may be adjusted downward
so that the signal from the transponder 702 may be distinguished
from the background noise.
[0062] Once adjustments are made to either, both, or neither of the
gain of the receiver and the signal strength of the transmitter
716, the transmitter 716 sends an interrogation signal to the RFID
transponder 702 to either encode or read the transponder 702. If
reading the RFID transponder 702, the adjusted gain (if it was
adjusted) of the receiver 714 will facilitate the reading of the
response signal from the RFID transponder and if writing to the
transponder 702, a fixed offset is applied to the "write" signal
depending upon the signal to noise ratio.
Processes of Use of the Invention
[0063] FIGS. 8 and 9 describe processes for use of the embodiments
of the system described above for adjusting the signal strength of
the transmitter 716 portion of the transceiver 708. The process of
FIG. 8 starts at Step 800. Then at Step 802 a transponder is
interrogated with a first electromagnetic signal. At Step 804, a
response signal is received from the interrogated transponder,
where the response signal was caused to be transmitted from the
transponder by the first electromagnetic signal. At Step 806, the
SNR of the response signal is determined. At Step 808, the SNR as
determined in Step 806 is used to adjust the strength of a second
electromagnetic signal that is used to either read or to encode the
transponder. The process ends at Step 810. The process of FIG. 9
begins at Step 900. At Step 902 a sample size of a plurality of
RFID transponders to be read or encoded is determined. This sample
size may be based on statistical sampling techniques, as are known
in the art. The sample size may also be arbitrarily or randomly
determined as well. A sample size could include all of the
plurality of transponders to be read or encoded, or it could only
be one of the plurality of transponders. Also, it could be
determined to sample, for example, only every other transponder, or
every third transponder, etc, with the strength of the
interrogation signal adjusted after each sample's SNR is
determined. At Step 904, according to the determined sample size of
the plurality of transponders, the SNR is determined for each
transponder in the sample. Based on the sample size, at Step 906 an
average SNR is determined which is used to calibrate the strength
of an electromagnetic signal used to encode or read the plurality
of RFID transponders. At Step 908, the power of an encoding or
reading signal used to encode or read the plurality of transponders
is adjusted based on the average signal-to-noise ratio using the
adaptive control module. The process ends at Step 910.
[0064] FIGS. 10 and 11 describe processes for use of the
embodiments of the system described above for adjusting the gain of
the receiver 714 portion of the transceiver 708. The process of
FIG. 10 starts at Step 1000. At Step 1002 a transponder is
interrogated with a first electromagnetic signal. At Step 1004, a
response signal is received from the interrogated transponder,
where the response signal was caused to be transmitted from the
transponder by the first electromagnetic signal. At Step 1006, the
SNR of the response signal is determined. At Step 1008, the SNR as
determined in Step 1006 is used to adjust the gain of the receiver
714 portion of the RFID transceiver 708 such that it is better able
to detect a signal transmitted from the transponder 702. The
process ends at Step 1010.
[0065] The process of FIG. 11 begins at Step 1100. At Step 1102, a
sample size of a plurality of RFID transponders to be read or
encoded is determined. This sample size may be based on statistical
sampling techniques, as are known in the art. The sample size may
also be arbitrarily or randomly determined as well. A sample size
could include all of the plurality of transponders to be read or
encoded, or it could only be one of the plurality of transponders.
Also, it could be determined to sample, for example, only every
other transponder, or every third transponder, etc, with the
strength of the interrogation signal adjusted after each sample's
SNR is determined. At Step 1104, according to the determined sample
size, the SNR is determined for each transponder in the sample.
Based on the sample size, at Step 1106 an average SNR is determined
which, at Step 1108, is used to calibrate the gain of the receiver
portion 714 of an RFID transceiver 708 that is to receive a signal
transmitted from one or more of the plurality of transponders in
response to an electromagnetic signal. The process ends at Step
1110.
[0066] FIG. 12 is a process for encoding or reading information on
an RFID transponder by adjusting either or both of the signal
strength used to interrogate the transponder and the gain of a
receiver used to receive a signal from the transponder. The process
of FIG. 12 starts at Step 1200. At Step 1202 a transponder is
interrogated with a first electromagnetic signal. At Step 1204, a
response signal is received from the interrogated transponder,
where the response signal was caused to be transmitted from the
transponder by the first electromagnetic signal. At Step 1206, the
SNR of the response signal is determined. At Step 1208, it is
determined whether the transceiver's gain, signal strength, or both
gain and signal strength require adjustment in order for the
transceiver to better communicate with the transponder. If, at Step
1208, no adjustment is required, then the process ends at Step
1210. If an adjustment is required, then the process continues to
Step 1212 where it is determined whether to adjust only the gain of
the receiver portion of the transceiver, adjust only the signal
strength of the transmitter portion of the transceiver, or adjust
both the gain and the signal strength of the transceiver. If it is
determined at Step 1212 to adjust only the signal strength of the
transmitter portion of the transceiver, then the process goes to
Step 1214, where the adaptive control module adjusts the power of
the interrogation signal in accordance with the SNR. If it is
determined at Step 1212 to adjust only the gain of the receiver
portion of the of the transceiver, then the process goes to Step
1216, where the adaptive control module adjusts the gain of the
receiver such that the RFID transceiver is better able detect a
signal transmitted from the transponder. If it is determined at
Step 1212 that both the gain and the signal strength are to be
adjusted, then the process goes to Step 1218 where the adaptive
control module adjusts both the gain of the receiver portion of the
transceiver and the signal strength of the transmitter portion of
the transceiver.
CONCLUSION
[0067] Many modifications and other embodiments of the invention
set forth herein will come to mind to one skilled in the art to
which this invention pertains having the benefit of the teachings
presented in the foregoing descriptions and the associated
drawings. Therefore, it is to be understood that the invention is
not to be limited to the specific embodiments disclosed and that
modifications and other embodiments are intended to be included
within the scope of the appended claims. For example, the
embodiments of the invention have been described as being
incorporated into a printing device, but it is to be appreciated
that this is just one of many uses of the systems and methods of
the present invention. Other applications include the inventions
use in any instance where RFID transponder encoding or reading
occurs including the processing of more than one RFID transponder
substantially concurrently. For instance, it is contemplated that
an embodiment of the invention is to process a plurality of RFID
transponders by substantially simultaneously transmitting a first
electromagnetic signal to the RFID transponders and then
determining the signal to noise ratio of each RFID transponder as
it responds to the first electromagnetic signal. The determined SNR
is then use to adjust the signal strength of a second
electromagnetic signal and/or the gain of the transceiver. Although
specific terms are employed herein, they are used in a generic and
descriptive sense only and not for purposes of limitation.
* * * * *